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ATSDR's PHAs are exposure, or contact, driven. A release of a hazardous wastedoes not always result in human exposure. Rather, people are exposed to acontaminant such as those identified at the INEEL site only if they come in contactwith it; they might be exposed by breathing, eating, or drinking a substancecontaining the contaminant, by skin contact with a substance containing thecontaminant, or from close proximity to gamma emitters.

Site Background

Idaho National Engineering and Environmental Laboratory (INEEL) is situated on theupper Snake River Plain in southeastern Idaho. The site spans Butte, Bingham,Bonneville, Clark, and Jefferson Counties, encompassing 890 square miles. INEEL isowned by the federal government, managed by the US Department of Energy (DOE), andoperated by Bechtel BWXT.

In the 1940s, the federal government began using the site to test refurbished naval gunsand other ordnance and to research and develop nuclear reactors and related equipment.In 1975, the site was designated a national environmental research park to advance thescience and technology related to environmental characterization and restoration of sitespreviously used for nuclear operations. DOE made INEEL the lead laboratory indeveloping new environmental technologies for DOE site cleanup and wastemanagement.

As a result of past operations and disposal practices, chemical and radiological materialshave been released to the environment. Since 1986, about 500 potentially contaminatedsites have been identified at INEEL under an Environmental Restoration Program. Thesources of the contamination include spills, abandoned tanks, septic systems, percolationponds, landfills, and injection wells. Because of the presence of certain contaminants atINEEL, the US Environmental Protection Agency (EPA) added INEEL to its NationalPriorities List in November 1989. Site investigations and remediation are underway.

ATSDR Conclusions

According to the information reviewed by ATSDR, under normal operating conditions, INEEL poses no past, current, or future apparent public health hazard for the surrounding community from groundwater, surface water runoff, soil, biota , or air. ATSDR has focused its review on data generated from 1987 to 2000. For exposure prior to 1987, the National Center for Environmental Health (NCEH) of the Centers for Disease Control and Prevention (CDC) is conducting a dose reconstruction. ATSDR will review the information, when the dose reconstruction is complete.

In drawing its conclusion about potential public health hazards now or in the future, ATSDR considered the following:

  • There are currently effective restrictions on access to each contaminated site at INEEL. In addition, a large part of INEEL is open space that creates a buffer zone (of at least 6 miles) between INEEL operational areas and the nearest neighbors.

  • No site-related contaminants are currently, or will in the future, be accessible to the public on or off site at levels that would cause health effects. No adverse health effects are expected because the concentrations of the contaminants found are below comparison values.

  • DOE continues cleanup activities at INEEL, with oversight provided by the State of Idaho Department of Environmental Quality and EPA.

Community Concerns

In collecting and evaluating residents' public health concerns, ATSDR obtained theassistance of the INEEL Health Effects Subcommittee, the Idaho Bureau ofEnvironmental Health and Safety, and the Cancer Data Registry of Idaho. The publichealth concerns obtained to date and ATSDR's response to them are presented andanalyzed in the main body of this public health assessment.

On-Site Drinking Water

For potential public health hazards in the past, ATSDR determined that visitors could have been exposed to VOCs and tritium when they drank water drawn from certain INEEL drinking water wells. This exposure, however, would not have caused any adverse health effects. INEEL continues to test the water supply to ensure that it meets safe drinking water requirements.

Health Outcome Data

Residents raised questions about excessive cancer rates and the occurrence of birth defects, both of which they believed to be related to environmental releases from the site in six counties in the vicinity of INEEL (Bannock, Bingham, Bonneville, Butte, Clark and Jefferson). ATSDR's evaluation of cancer rates for the counties of concern indicated that the types of cancers commonly associated with radiological and chemical exposures are within the range of what would be expected according to comparisons with cancer rates in the state of Idaho as a whole. Rates of certain cancers, cases, or deaths were less than expected, while some were greater than expected. In most instances, the differences were not statistically significant. Most of the increases in cancer rates were likely a result of random variability, since there did not appear to be any consistent increases across counties or within counties (e.g., although breast cancer incidence was significantly increased in Clark County, it was significantly decreased in the more populous Bingham County, compared to the incidence in the rest of the state). ATSDR obtained the assistance of the INEEL Health Effects Subcommittee, the Idaho Division of Health (Bureau of Environmental Health and Safety and the Center for Vital Statistics and Health Policy), and the Cancer Data Registry of Idaho.

1961 SL-1 Reactor Accident

Public concern was also voiced about a nuclear accident on January 3, 1961, which resulted in an air release at the site's Reactor Testing Station. The cause of the accident was most likely operator error. Three employees were exposed to radiation at lethal levels (all of the employees actually died from immediate non-radiation physical trauma). According to calculations conducted at the time, approximately 99.99% of the total fission product inventory in the core was retained inside the reactor building, even though it was not designed as a containment facility. Therefore, elevated air levels of fission products have not migrated off-site and have not resulted in radiation exposures or doses to the public above levels that would cause adverse health effects. ATSDR has not received reports of health effects related to this accident; however, if data become available suggesting that health effects did occur, the agency will reevaluate the need for follow-up activities.


Site Description and History

INEEL is on the upper Snake River Plain in southeastern Idaho, at an average elevationof 4,900 feet above sea level. The site spans 890 square miles in Butte, Bingham,Bonneville, Clark, and Jefferson Counties, extending 39 miles from north to south, with a36-mile width at the southern boundary. INEEL is bordered on the north and west bythree mountain ranges and on the south by three large buttes. Only about 6% of theproperty contains buildings or other structures; the remaining 94% of the site isundeveloped and open land. Figure 1 shows the location of INEEL (ESRF 1998).

INEEL is owned by the federal government, but it is operated by Bechtel BWXT forthe DOE (INEEL 2001a). Other administrators of the site are or have included DOE'sIdaho Operations Office (DOE-ID), the Idaho Branch Office of Pittsburgh NavalReactors (IBO), and DOE's Chicago Operations Office (DOE-CH), whose supportingcontractors are Bechtel BWXT, Westinghouse Electric Corporation (WEC), andArgonne National Laboratory (ANL), respectively. DOE-ID is responsible forenvironmental control and management of INEEL.

The site was used by the federal government in the 1940s to test refurbished naval gunsand other ordnance. In 1949, the site was designated as the National Reactor TestingStation by the Atomic Energy Commission (AEC). INEEL's mission was to conductnuclear reactor research and to develop nuclear reactors and related equipment. Over theyears, scientists constructed 52 test reactors at INEEL. Most test reactors were phased outwhen their missions were completed. Three reactors still operate at INEEL: the AdvancedTest Reactor (ATR) in the Test Reactor Area (TRA), which produces a large amount ofthe nation's medical and industrial isotopes; the ATR Critical Flux in the TRA; and theNeutron Radiograph in the Argonne National Laboratory-West facility.

During the past 50 years, INEEL has also been used for radioactive waste disposal andstorage. Some of the waste has been created at INEEL as part of its ongoing operations,and some has been shipped to INEEL from other US sites (DOE 1999).

In 1974, the National Reactor Testing Station was renamed the Idaho NationalEngineering Laboratory. DOE designated the site as the lead laboratory for developingnew environmental technologies for DOE site cleanup and waste management. OnJanuary 29, 1997, the site was renamed the Idaho National Engineering andEnvironmental Laboratory to reflect the growing environmental program.

Today, DOE uses INEEL to "develop, demonstrate, deploy, and transfer advancedengineering technology and systems to private industry" (INEEL 2001a). Thefollowing are a few of the major DOE programs currently ongoing at INEEL:

  • Providing test irradiation services and producing radioisotopes for medicaland commercial uses at the ATR.

  • Conducting light water-reactor safety testing and research.

  • Managing hazardous, radioactive, mixed wastes, and spent nuclear fuel.

  • Conducting environmental restoration.

Environmental Restoration and Management

INEEL's mission has focused on providing research and engineering support to the military, commercial, and governmental segments of the US economy. Over the years, this mission has meant applying nuclear power to commercial and naval use; reprocessing spent nuclear fuel; storing nuclear waste; and currently, remediating and managing waste generated at INEEL.

Some site operations have released non-radiological and radiological materials to the surrounding soil or air. Some of this contamination has reached the underlying groundwater.

Monitoring activities were initiated at INEEL to provide information about the pathways that might expose INEEL workers and the general public to site contaminants. Because of the nature of the activities at INEEL, radionuclides were the major contaminants analyzed during the early monitoring efforts. In 1984, DOE and EPA agreed to establish a non-radiological and radiological environmental monitoring program to further protect human and environmental health and ensure compliance with applicable federal, state, and local regulations (LMITCO 1998).

An Environmental Restoration Program was established at INEEL to clean up environmental contamination and decommission facilities that are no longer supporting INEEL's mission. Cleanup is conducted under a Federal Facility Agreement and Consent Order agreed upon by DOE, EPA, and the State of Idaho, in accordance with the Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), also known as Superfund (DOE 1995). Since 1986, about 500 potentially contaminated sites have been identified under the Environmental Restoration Program. Sources include spills, abandoned tanks, septic systems, percolation ponds, landfills, and injection wells. Because of the presence of certain contaminants, EPA added INEEL to its National Priorities List in November 1989 (ESRF 2000).

INEEL Site Location
Figure 1. INEEL Site Location

Location of INEEL and Selected Facilities
Figure 2. Location of INEEL and Selected Facilities

INEEL is divided into 10 Waste Area Groups (WAGs), each containing multiple operableunits (OUs) and solid waste management units (SWMUs), some of which may overlap.An OU is a group of previously identified hazardous waste sites that share similarenvironmental media and geographic distributions. Eighty-three OUs have been identifiedat INEEL. Nine of the WAGs correspond to INEEL's major facilities. The tenth WAGincludes the aquifer underlying the site and other miscellaneous areas (see Figure 2).Appendix C describes the WAGs in greater detail, and Table 1 summarizes the primarychemicals used at each WAG (DOE 1995).

Table 1.

Waste Area Groups at INEEL
WAG No. Location/Description Chemicals Used/Disposed Of
1 Test Area North (TAN) 10 operable units (OUs) and 63 solid waste management units (SWMUs) Acids, petroleum products, asbestos, fission products, organic wastes (including TCE), and heavy metals
2 Test Reactor Area (TRA), 13 OUs and 49 SWMUs Organic wastes, petroleum products, fission products, and heavy metals
3 Idaho Nuclear Technology Engineering Center (INTEC), 13 OUs and 66 SWMUs Organic wastes, petroleum products, fission products, transuranic radionuclides, asbestos, acid salts, and heavy metals
4 Central Facilities Area (CFA) 13 OUs and 38 SWMUs Ordnance, salts of acids, petroleum products, heavy metals, fission products, asbestos, and organic waste
5 Power Burst Facility/Auxiliary Reactor Area (PBF/ARA), 13 OUs and 43 SWMUs Fission products, petroleum products, heavy metals, and organic wastes
6 Experimental Breeder Reactor-1/Boiling Water Reactor Experiment (EBR-1) 5 OUs and 20 SWMUs Heavy metals, organics, fission products, and petroleum products
7 Radioactive Waste Management Complex (RWMC), 14 OUs Fission products, transuranic radionuclides, organic wastes, salts of acids, ordnance, and heavy metals
8 Naval Reactors Facility (NRF) 8 OUs and 54 SWMUs Heavy metals, organics, petroleum products, and radionuclides
9 Argonne National Laboratory-West (ANL-W), 4 OUs and 14 SWMUs Heavy metals, fission products, petroleum products, and dioxins/furans
10 Miscellaneous Units and Snake River Plain Aquifer (SRPA), 4 OUs and 13 SWMUs Salts of acids, fission products, organic wastes, and ordnance

INEEL's Environmental Restoration Program further identified 26 specific areasthroughout the 10 WAGs as requiring environmental investigation. As of January 2000,environmental investigations have begun at 21 areas. DOE, EPA, and the State of Idahohave reached a final cleanup decision, known as a Record of Decision (ROD), at 19 ofthe areas, and they have completed cleanup at 12 (INEEL 2001b).

Numerous technologies are employed to remediate INEEL, including containment,immobilization, and physical, thermal, chemical, and biological processes. Some ofthe areas have yet to be investigated, including the buried waste at the RWMC(WAG 7), soil contamination at INTEC tank farms (WAG 3), and site-widegroundwater and SRPA contamination.

INEEL established an Environmental Surveillance Program to monitor the level andassess the impact of pollutants from INEEL operations on the environment (BWXT2000). The management and operating contractor, currently Bechtel BWXT, isresponsible for the on-site portions of the program. Two components exist within theEnvironmental Surveillance Program: the Waste Management Surveillance Program(WMSP) and the Site Environmental Surveillance Program (SESP). The WMSP monitorssoils, ambient air, direct radiation, biota, and surface water at the Radioactive WasteManagement Complex, the Waste Experimental Reduction Facility, the Mixed WasteStorage Facility, Test Area North, and the Organic Moderated Reactor Experiment, incompliance with DOE Order 435.1. The SESP monitors ambient air, soils, and directradiation beyond the boundaries of the individual waste management facility sites butwithin the borders of INEEL, in compliance with DOE Order 5400.5 (ESRF 1998).

In addition to the DOE contractor for INEEL, four other organizations monitor theenvironment in and around INEEL. The other organizations are: the US GeologicalSurvey, the Environmental Surveillance, Education and Research Program, the NationalOceanic and Atmospheric Administration, and the State of Idaho Oversight Program(part of the Idaho Department of Environmental Quality). These organizations workindependently of the DOE contractor to assess contaminant concern at INEEL. Theresults of their work provide quality assurance of and lends confidence to data collectedby the site contractors (ESRF 2000).

Environmental Management

INEEL has managed waste from on- and off-site sources for about 50 years. Most of thewaste and the resulting contamination was generated by Cold War activities (INEEL2001b). The types of waste managed range from radioactive waste (including transuranic,high-level, and low-level radioactive waste) to hazardous waste and industrial waste. TheGlossary in Appendix F includes definitions of the different types of radioactive wastestored/disposed of at INEEL. INEEL also handles DOE's spent nuclear fuel from thenational nuclear weapons complex (INEEL 2001b).

Demographics and Land Use

When assessing a site, ATSDR seeks to identify the people in the site's vicinity who are more likely than usual to be exposed to contamination, as well as populations (such as young children and the elderly) that are especially sensitive to exposure. To do so, ATSDR uses demographic (or population) information and land use information. Demographics also provide details on residential history in a particular area–information that helps ATSDR assess time frames of potential human exposure to contaminants. Demographic information for the residential areas surrounding INEEL is presented in this section. (Note that proximity, in itself, is not an adequate indicator of exposure to site-related contaminants. Whenever possible, proximity measures must be supplemented with environmental pathway information to permit evaluation of exposed populations.)

Today, INEEL is the largest employer in the area, with a workforce of approximately 8,100 people (ESRF 2000, INEEL 2000). The workforce includes about 400 federal employees, most of whom work for DOE-ID. Most of the other, non-federal employees work for or have worked for DOE contractors, including Bechtel (BWXT), Westinghouse Electric Corporation, and ANL (ESRF 1998). There are no permanent residents at INEEL or within a 10-mile radius of the operational center of the INEEL site.

The varied land use at INEEL includes the following broad categories: facility operations, general open space, grazing, and infrastructure. While 6 % of the INEEL site is developed, only about one-third of the developed area is used for facility operations in support of energy research and waste management activities.

A large portion of the site is open space that creates a buffer zone between INEEL operational areas and the nearest neighbors. Cattle and sheep graze on 300,000 to 350,000 acres (about 60%) of this buffer zone (DOE 1995). For the purpose of limiting any potential radionuclide contamination, animals are not allowed within 2 miles of any nuclear facility, and dairy cattle are not permitted. INEEL is a National Environmental Research Park. Public tours of the general facility and of a National Historic Landmark (Experimental Breeder Reactor-I) are available, and controlled hunting within a half-mile of the boundary fence is allowed. INEEL has several quarries, from which sand, gravel, pumice, silt, clay, and aggregate are extracted. These materials are used to build and maintain roads, construct facilities, bury wastes, and landscape (DOE 1995). Public roads and utility rights-of-way cross INEEL. However, public access to operation sites is restricted by fences, guard stations, and patrols.

Lands immediately beyond the boundaries of INEEL are desert, but some are irrigated for agricultural use. The closest towns to the boundaries of INEEL are Atomic City (population 25), 1 mile beyond INEEL's southern boundary; Mud Lake (population 179); and Tereton (population 100). Larger centers, such as Idaho Falls (population 43,929) to the east and Pocatello (population 46,080) and Blackfoot (population 9,646) to the southeast, are at least 20 miles from INEEL boundaries, even further from areas of contamination at INEEL's operational areas.

Farming is largely concentrated 50 to 70 miles northeast of the site. Large areas of agricultural land are also farmed in the Snake River Valley to the east and south of the site, although those areas are more than 30 miles from INEEL's RWMC, the operational area closest to the INEEL southern boundary.

Table 2 contains the demographic statistics for areas within 1, 5, and 10 miles of the nearest INEEL facility or building. As Table 2 notes, no one resides within one mile of any INEEL facility or building. Approximately 427 people reside within 10 miles of any INEEL facility or building. This population includes 46 children aged 6 years and younger, 72 females aged 15 to 44 years, and 44 adults aged 65 and older. Figure B-1 (Appendix B) shows the total population density in 1-, 5-, and 10-mile increments from INEEL facilities or buildings, and Figure B-2 shows the population density in 5, 10, 25-, and 50-mile increments from INEEL site boundaries.

Table 2.

INEEL Regional Demography
Demographic Variables Miles from Nearest INEEL Facility
1 5 10
Total Population 0 45 427
Racial Characteristics
White alone 0 45 385
Black alone 0 0 0
Am. Indian and Alaska Native alone 0 0 2
Asian alone 0 0 4
Native Hawaiian and Other Pacific Islander alone 0 0 0
Some Other Race alone     34
     Two or More Races     3
     Hispanic or Latino 0 1 44
Sensitive Populations
Children Age 6 and Younger 0 2 46
Females Age 15-44 0 4 72
Adults Age 65 and over Older 0 7 44
Other Variables
     Total Housing Units 0 29 188

Demographic Statistics Source: 2000 US Census.


What is exposure?ATSDR’s public health assessments are exposure, orcontact, driven. Chemical contaminants disposed orreleased into the environment have the potential tocause adverse health effects. However, a releasedoes not always result in exposure. People canonly be exposed to a chemical if they come in contactwith the chemical. Exposure may occur by breathing,eating, or drinking a substance containing thecontaminant or by skin (dermal) contact with asubstance containing the contaminant.When do health effects occur?Exposure does not always result in health effects.The type and severity of health effects that occur in anindividual from contact with a contaminant depend onthe properties of the chemical, the exposureconcentration (how much), the frequency and/orduration of exposure (how long), the route or pathwayof exposure (breathing, eating, drinking, or skincontact), and the multiplicity of exposure (combinationof contaminants). Once exposure occurs,characteristics such as age, sex, nutritional status,genetics, life style, and health status of the exposedindividual influence how the individual absorbs,distributes, metabolizes, and excretes thecontaminant. Together, these factors andcharacteristics determine the health effects that mayoccur as a result of exposure to a contaminant in theenvironment.Introduction

This section presents an evaluation of environmental data collected for the INEEL site.ATSDR evaluated these data to determine whether any contamination exists at levels thatnecessitate further evaluation (which in turn would determine if that contamination couldbe a public health hazard to the general public). Figure 3 describes the conservativeexposure evaluation process used by ATSDR.

If exposure was or is possible, ATSDR then considers whether chemicals were or arepresent at concentrations that might be harmful to people. ATSDR does this by screeningthe concentrations of contaminants in environmental media (e.g., groundwater or soil)against health-based comparison values (CVs) (Appendix A). CVs are chemicalconcentrations that health scientists have determined are not likely to cause adverseeffects, even when assuming very conservative/worst case exposure scenarios. Because CVs are not thresholds of toxicity, environmental levels that exceedCVs would not necessarily produce adverse health effects. If a chemical is found in theenvironment at levels exceeding its corresponding CV, ATSDR examines potentialexposure variables and the contaminant toxicology. ATSDR emphasizes that a publichealth hazard exists only if contact with harmful levels of contaminated media occurswith sufficient frequency and duration for harmful effects to occur.

Some of the comparison values used for screening by ATSDR scientists includeATSDR's Environmental Media Evaluation Guides (EMEGs), Reference Dose MediaEvaluation Guides (RMEGs), and Cancer Risk Evaluation Guides (CREGs), as well asEPA's Maximum Contaminant Levels (MCLs). MCLs are enforceable drinking water regulationsdeveloped to protect public health. CREGs, EMEGs, and RMEGs are non-enforceable,health-based comparison values developed by ATSDR as a way to screen environmentalcontamination for further evaluation. Appendix E discusses the basis for the comparisonvalues used in this evaluation.

ATSDR's Exposure Evaluation Process
Figure 3. ATSDR's Exposure Evaluation Process

Media-Specific Contamination

ATSDR reviewed non-radiological (chemical) and radiological data collected for groundwater, surface water, soil, air, and/or food in support of environmental monitoring at INEEL. ATSDR also reviewed information on ambient ionizing radiation exposures at the site. The material reviewed included quarterly, annual, and supplemental environmental reports for the 1950s through 1999.

This subsection summarizes environmental monitoring data for the different media by non-radiological and/or radiological contamination, and for ambient radiation at INEEL. Data tables 3 and 4 in the following text, as well as the tables in Appendix A, are also provided for media containing contaminants at levels exceeding comparison values. When they are available, ATSDR also evaluates off-site monitoring data. To harm human health, environmental contaminants must have a way to reach people and expose them. These exposure pathways are discussed in the "Pathways Analysis" section and summarized in Table 5. The potential for contaminants of concern that can reach people to cause illness is then evaluated in the "Public Health Implications Section".

For more information, see the appendices. Appendix E explains the different types of comparison values (CVs), Appendix F is a glossary of terms, and Appendix G discusses radiation and radioactive material. ATSDR presents two systems of radiological units of measurements: the Conventional System and the Systeme International. These units, other symbols, and abbreviations used in this document in radiological discussion are noted in the key below:

System Unit Parameter/Description
Units of Radioactivity (Conventional Units) picocurie, pCi The curie (Ci) is the basic unit of radioactivity. The pCi is 1,000,000,000,000 times smaller than one Ci.
milliroentgens, mR Radiation exposure is expressed in terms of roentgens (R). One mR is 1,000 times smaller than one R.
mrem Dose is given in units "roentgens equivalent man", or rems. One mrem is 1,000 smaller than one rem.
Units of Radioactivity (Systeme International) becquerel, Bq The basic units of activity is the becquerel (Bq). The number of curies must be multiplied by 3.7 x 1010 to obtain equivalent number of Bqs.
millisievert, mSv The sievert (Sv) is the unit of dose equivalent. One mSv is 1,000 times smaller than one SV. One mSv = 100 mrem.

Feature Symbol Description
Uncertainty Measurements ± Radioactivity measurements are given with a range of uncertainty denoted by "±" because of the statistical nature of the decay events. Usually data from the INEEL are presented in the form of one standard deviation which gives one (1) confidence in 68 of 100 cases that the true level of radioactivity falls between the measured concentration plus the uncertainty value and the measured concentration minus the uncertainty value. In the past, the INEEL used two standard deviations (95 out of 100) as a criterion for determining whether the measured value was valid. The INEEL now uses three standard deviations as the criterion, which is 997 cases out of 1000. Uncertainty values are available for some radiological measurement but not for all–presented in this document.
Negative Numbers as Results   Negative results are presented where the measured result is less than the preestablished average background concentration. Reporting these values better enables a scientist to observe trends or bias in the data.


The Snake River Plain Aquifer (SRPA) underlying INEEL is one of the most productiveaquifers in the United States, serving as the primary drinking water source for SouthernIdaho. The aquifer–or water-saturated zone–lies between 200 to 1000 feet belowground surface. It is made up of rock units that consist primarily of basaltic lava flowsand interbedded sedimentary deposits. Water in this aquifer moves rather fast comparedto other aquifers, primarily in the south-southwest direction through fractures in thesolidified basalt lava flows, at an estimated rate of about 6 to 10 feet per day. Some localgroundwater flow beneath INEEL is more complex and variable, because it is influencedby production wells, recharge from the Big Lost River, by percolation and sewage ponds,by areas of low aquifer transmissivity, and possibly by pumping from the productionwells. Ground water velocities on site range from about 0.5 ft/day around Test AreaNorth (TAN) to greater than the 10 ft/day in the vicinity of the Idaho Nuclear Technologyand Engineering Center (INTEC).

Approximately 470 billion gallons of water flow underneath INEEL annually. CurrentINEEL activities use an average of 1.6 billion gallons of water from the aquifer eachyear, or less than one half of 1% of the estimated volume of water passing beneath thesite. Total INEEL water consumption from reasonably foreseeable activities, includingwaste processing activities, could increase by 189 million gallons per year. Thisconsumption would be a 12% increase in water withdrawn from the SRPA, but the newamount would still be less than 1% of the water passing under the site (DOE 1999).

A significant amount of recharge to the SRPA at INEEL comes from the intermittentflows of the Big Lost River, of irrigation water, and of groundwater inflow fromadjoining mountain drainage basins. Most of the groundwater is recharged in the uplandsto the northeast before it moves southwest through the aquifer to be discharged to springsalong the Snake River near Hagerman. Lesser amounts of water come from localprecipitation on the plain. Part of the precipitation evaporates, but part infiltrates into theground surface and percolates downward to the aquifer.

The vadose—or unsaturated—zone extends down from the ground surface to the watertable (the top of the SRPA). The water table ranges from about 200 ft to over 900 ftbelow ground surface. The subsurface materials in the vadose zone are generally notsaturated: they contain both air and water. It is believed that the vadose protects theunderlying groundwater by filtering many contaminants through adsorption, slowing thetransport of contaminants, or breaking down contaminants by natural decay processes(DOE 1995).

Perched water zones have formed beneath portions of INEEL. These are zones ofgroundwater that sit on relatively impermeable layers of sediment or clay (ESRF 2000).There are known perched water zones at four INEEL facilities: INTEC, TRA, TAN, andthe RWMC. The systems formed over time from water trickling down through thepercolation ponds and from the sewage treatment plant lagoons, precipitation, floodingevents, and particularly during periods of dryness of the Big Lost River (DOE 1999). Theperched water zones are too small ever to be tapped for drinking water, and they do notextend far enough from source areas ever to reach off-site communities or their drinkingwater supplies. Perched water zones sometimes protect the SRPA from contamination hotspots.

Groundwater serves as the primary source of drinking for INEEL. Currently, the watersystem at INEEL relies on 17 production wells and 10 distribution systems (ESRF2000).

The US Geological Survey (USGS) began a groundwater monitoring network at INEELin 1949, before nuclear-reactor testing facilities were developed at the site. During theearly monitoring years, periodic water-level and water-quality data were collected fromthe network to describe the occurrence, movement, and quality of SRPA water, in orderto characterize INEEL water resources before the development of nuclear reactor testingfacilities (USGS 1997). The USGS has maintained a formal comprehensive groundwatermonitoring program at INEEL to describe the type and amount of contamination ingroundwater beneath the site.

The USGS INEEL Project Office currently oversees 125 aquifer monitoring wells locatedon-site in areas of detailed study, specifically the TRA, the Idaho Nuclear TechnologyEngineering Center (INTEC) [ formerly the Idaho Chemical Processing Plant (ICPP)], theRWMC, and the TAN, and off-site south, southeast, and southwest of the INEELboundary. In addition, 55 sites between the southern site boundary and Hagerman aremonitored (ESRF 1998). The wells installed in the SRPA are screened at different depths:from about 200 feet below ground surface in the northern part of INEEL to more than 900feet below ground surface in the southeastern part. An additional 45 wells are availablefor sampling perched water zones. (Water samples from surface water sites at or nearINEEL and from wells in perched groundwater zones are also analyzed to document thechemical quality of the water that recharges the aquifer.)

Today, USGS, DOE, and other organizations monitor groundwater from wells on andnear INEEL on schedules ranging from monthly to yearly, depending on theinformation needed for specific areas (USGS 1997, INEEL 2000). The monitoringallows scientists to track plumes of contamination beneath the INEEL facility.Collected samples are then analyzed for 60 volatile organic compounds (VOCs), metals,trace elements, and radionuclides, as well as for selected chemical and physicalparameters as needed. The various organizations conduct special studies to identify anyproblems with the groundwater of the SRPA at facilities within INEEL at which pastreleases are suspected (ESRF 1998).

INEEL established a centralized drinking monitoring water program (DWP) in 1988 atmost on-site facilities. The DWP, as well as other organizations, monitors 17production/drinking water wells and 10 distribution systems for radiological, non-radiological (chemical), and bacteriological contaminants (LMITCO 1998). The NavalReactors Facility (NRF) and the Argonne National Laboratory-West (ANL-W) maintainseparate drinking water monitoring programs (ESRF 1998).

The ESRF and the Oversight Program also monitor drinking water quarterly,semiannually, and annually at on-site locations and in off-site communities near the siteboundary and at a distance. These samples are tested for gross alpha and betaradioactivity and tritium. With the use of gamma spectroscopy, they are also tested for Sr-90, Tc-99 and other selected ions (ESRF 2000).

Waste disposal practices over the past 50 years have resulted in contaminants seepingdown to the groundwater of the SRPA and forming localized contaminant plumesbeneath portions of the INEEL site. The contaminants originated from wastewater thatwas discharged into injection wells or disposed of into unlined infiltration or evaporationponds in certain operational areas of INEEL, including INTEC and TAN, and fromleakage of buried waste at the RWMC. Some contamination has trickled down into theperched water zones, most notably in the TRA area (INEEL 2000). At the time ofconstruction, the waste injection wells were thought to be the best means to reducehuman contact with waste.

Increased concern about the environment prompted changes in disposal practices atINEEL. These changes included elimination of wastewater injection in 1986, wastewatermonitoring, and improved wastewater treatment system, such as the use of infiltrationponds, which allow the wastewater to slowly move through soil before reaching thegroundwater.

Through routine monitoring of its groundwater network, elevated levels of VOCs,metals, semivolatile organic compounds (SVOCs), and polychlorinated biphenyls(PCBs) have been measured in the SRPA and in the perched aquifers beneathINEEL. Table A-1 provides information about these contaminants, their maximumconcentrations as detected in on-site monitoring wells, and the location of thosedetections.

What are VOCs ?Volatile organic compounds (VOCs)are a group of organic chemicalshaving similar physical properties.These chemicals were detected inhigh concentrations beneath certainareas of INEEL. VOCs easilyevaporate when exposed to air.Chemicals in this group includetrichloroethylene (TCE), benzene,tetrachloroethylene (PCE) andcarbon-tetrachloride. At INEELthese chemicals were used ascleaning solvents for degreasing.Much of the VOCs in the wasteareas were from off-site waste thathad been brought in from otherfacilities such as Rocky Flats fordisposal.Of the contaminants detected, the VOCs carbontetrachloride, 1,1,1-trichloroethane (1,1,1-TCA),and trichloroethylene (TCE) were amongcontaminants detected most frequently and in thehighest concentrations. The highest levels of VOCswere measured in groundwater samples collectedfrom the RWMC, TAN, and TRA facilities atINEEL. Note that chemical constituents associatedwith INEEL operations have not migrated beyondINEEL boundaries. Groundwater contamination inthe SRPA and the perched aquifers is discussed ingreater detail below.

The RWMC is situated on 168 acres, of which 97acres constitute the actual disposal site, called theSubsurface Disposal Area. The RWMC is in thesouthwestern portion of the INEEL site, about 6miles from the INEEL southern boundary. Since itsestablishment in the early 1950s, the RWMC hasserved as a controlled area for storage of solidradioactive and chemical defense wastes. Thefacility is also home to research and developmentprojects dedicated to shallow land burial technologyand alternate ways of removing, reprocessing, and repackaging transuranic wastes.

Solid and liquid chemical and radioactive wastes were buried in trenches and pits withinsections of RWMC. Drums containing degreasing solutions and solvents were alsoburied. Many of the drums have deteriorated, releasing their contents to the surroundingsoil over time. It is estimated that about 88,400 gallons of waste were buried before 1970:about 24,400 gallons of carbon tetrachloride, 39,000 gallons of lubricating oil, and 25,000gallons of other organic compounds, including 1,1,1-TCA, TCE, perchloroethylene,toluene, and benzene. Since 1970, a layer of sediment has been added to the trenches tohelp impede any waste constituents from leaching into the underlying groundwater(ESRF 1999).

Groundwater investigations have identified VOCs at levels above ATSDR's CVs andEPA's drinking water standards in the SRPA beneath the RWMC. For example, 1,1,1-TCA was detected at levels up to 6,800 parts per billion (ppb), above ATSDR's CVand EPA's MCL of 200 ppb. VOC concentrations had decreased by 1998; still, onewell (90) contained TCE (360 ppb) and tetrachloroethylene (PCE) (50 ppb) at levelsabove their MCLs (ESRF 2000).

High levels of VOCs were also detected in the perched water samples collected 70 feetbelow the surface of Pit 9. The maximum concentration of carbon tetrachloride wasmeasured at 8,900 ppb, but the level was below 1,000 ppb at the pit boundary and at traceamounts at wells further downgradient from the RWMC. No one is drinking from theperched aquifer contaminated with carbon tetrachloride because INEEL's perchedaquifers are all too small to supply facilities with drinking water.

The Record of Decision (ROD) for the RWMC signed by DOE, EPA, and the State ofIdaho in December 1994 selected vapor vacuum extraction with treatment as the mostappropriate remedial action. The treatment was specifically intended to removecontamination from the vadose zone, the area between ground surface and the top of thewater table. Since the treatment began in 1996, more than 78,000 pounds of VOCs havebeen removed or destroyed (ESRF 2000; INEEL 2000). Ongoing efforts continue toremove and treat VOCs extracted from the vadose zone.

The TAN, located approximately 12 miles from INEEL's eastern boundary, consists ofseveral facilities designed for handling, storing, examining, and conducting researchand development on spent nuclear fuel. The facilities supported research of the 1979Three-Mile Island incident and include one of the world's largest storage pools. Themajor facilities at TAN include the Contained Test Facility (CTF), the TechnicalSupport Facility (TSF), the Loss of Fluid Testing (LOFT) facility, and the WaterReactor Research Test Facility (WRRTF). From 1953 to 1972, chemical, low-levelradioactive, and sanitary wastewater was discharged at the TAN into the aquiferthrough a 310-foot deep injection (disposal) well. In 1972, the injection well wasreplaced by a 35-acre infiltration pond.

USGS investigations revealed that high levels of VOCs had entered the groundwaterbeneath the TAN area. TCE and PCE were measured at levels up to 32,000 and 110 ppb,respectively, both above their ATSDR CVs of 5 ppb for each. A VOC plume has alsocontaminated drinking water wells used by TAN employees (ESRF 1998). (See thedrinking water discussion below.)

DOE began cleaning up the injection well in 1993. In 1994, DOE initiated a pump-and-treat interim remedial action to remove TCE from the groundwater of the SRPA. Sludgehad been removed in 1990, but not before TCE had settled into pools of dense, non-aqueous phase liquid (DNAPL) below the SRPA. After months of operations, however,the TCE levels were higher than expected. The DNAPL pools continued to feed TCE tothe plume; however, the TCE concentration in the plume was kept from rising bybiodegradation caused by microorganisms from the injection well sewage. A ROD signedin August 1995 called for reducing the contamination levels to below the MCL of 5 ppbwithin 100 years. As a separate interim action, the treatment plant has been used toprovide hydraulic containment of the contaminants. Bacteria in the remaining injectionwell sludge continues to degrade the TCE, bringing the concentration closer to the MCL.

The TRA is located in the southwestern portion of INEEL, about 5 miles northwest ofthe CFA. The area was originally established in the early 1950s to conduct experimentsassociated with developing, testing, and analyzing materials used in nuclear and reactorapplications. The TRA houses the Advanced Test Reactor (ATR), which produces aneutron flux that simulates radiation effects on materials and fuels.

Starting in the late 1950s and the early 1960s, chemical, low-level radioactive, andsanitary wastewater was discharged to infiltration and evaporation ponds at the TRA.Between 1964 and March 1982, non-radioactive wastewater from cooling-toweroperations at the TRA was also injected into a disposal well in the SRPA. After March1982, this wastewater was discharged to two cold-waste infiltration ponds, and the wellhas been used as an observation well.

A perched water system has formed beneath the TRA from water percolating downthrough the disposal ponds. The perched water is a groundwater zone that sits on a layerof clay located about 330 feet above the SRPA. This layer of clay ultimately impedeswater from passing through (ESRF 1998). Note that perched water aquifers may not belarge enough or permeable enough to be used as a major source of drinking water, butmay still be tapped locally (a few households) for a drinking water source, and can stillcontain contaminants that may represent a future threat to the SRPA. Nevertheless, since1993, various agencies have been routinely monitoring water quality of the perchedaquifer to determine whether any actions are needed (ESRF 2000).

As discussed, SRPA groundwater beneath certain portions of the INEEL site has becomecontaminated with VOCs and metals. The DWP routinely tests drinking water fromproduction wells and distribution systems at INEEL for chemicals, including VOCs andmetals, to ensure that the water is safe for drinking. Monitoring to date has shown that theVOC contamination has affected several production wells at the RWMC and TANfacilities. Table 3 summarizes contaminant concentrations that exceed CVs/MCLs.

Table 3.

Maximum Concentrations of Non-Radiological Contaminants in Drinking Water Supply Wells
Contaminant Drinking Water Wells ATSDR CV/ EPA MCL
Maximum Conc. Location Date
Carbon Tetrachloride 5.5 ppb RWMC #1 10/1995 5 ppb/5 ppb
Trichloroethylene 15 ppb TSF #1 9/1996 5 ppb/5 ppb

Source: ESRF 1996.
MCL = EPA's maximum contaminant level; ppb = parts per billion.

As Table 3 indicates, the VOC carbon tetrachloride was detected at levels up to 5.5 ppb (just slightly above ATSDR's CV and EPA's MCL of 5 ppb) in a sample collected in 1995 from the RWMC #1 well at the RWMC facility. The concentrations reaching consumers, however, were much lower than the concentration detected at the wellhead.

Water collected from RWMC #1 also contained 1,1,1-TCA (0.6 ppb) and TCE (1.8ppb), but at levels below the screening comparison values (ESRF 1996). Carbontetrachloride levels in RWMC #1 increased slightly in 1996 but in 1997 decreased tolevels just below comparison values. Again, carbon tetrachloride levels in the RWMCdistribution system were lower than levels in the well (ESRF 1998).

Production wells at the TAN were also affected by VOCs. TCE was detected in 1987 atlevels averaging 6.1 ppb (exceeding EPA's MCL of 5 ppb) in wells TSF #1 and TSF #2.Even though distribution system concentrations were not found to exceed the MCL,bottled water was provided to the approximately 100 workers in this area as a precautionuntil an air-stripping system was installed in 1988. Concentrations at TSF #1 againexceeded the MCL throughout 1995 (at levels ranging from 7.8 to 12.9 ppb) and reachedlevels up to 15 ppb in 1996. The water samples from the distribution system, however,met safe drinking water standards. TSF #1 was taken off line during the third quarter of1997. TSF #2 is still being used (ESRF 2000; LMITCO 1998).

Note again that water drawn from INEEL production wells is diluted when it is mixedand then fed into a system of pipes that leads to water taps on INEEL. Because of thisdilution effect, drinking water reaching workers has never been found to contain VOCs atlevels exceeding the MCL, even though water in the RWMC or TAN production wellshas reached levels about 10% to 22% above the MCL. INEEL will continue to routinelymonitor its production wells to ensure that the water meets safe drinking water standards.

Groundwater samples are collected annually to determine whether substances generatedby INEEL facilities would migrate through the SRPA to the Snake River in the TwinFalls-Hagerman area. This Twin Falls-Hagerman area is referred to as the Magic Valleyarea. The SRPA supplies most of the water that supports the Valley's farming industry aswell as most of the region's drinking water.

Monitoring to date has detected VOCs and nitrates in off-site wells, but at low levels. Inall likelihood, this contamination has not originated from INEEL. Possible local sourcesof the low detected levels of VOCs and nitrates in the off-site groundwater samplesinclude agricultural fertilizers, effluent from animal-feeding operations and food-processing industries, and septic tanks (ESRF 2000).

What radionuclides were detected ingroundwater at INEEL?Tritium and strontium-90 areradionuclides that were frequentlydetected in groundwater at INEEL.These radionuclides were contained inwastewater that was disposed of ininjection wells or into infiltrationponds at the INTEC, TRA, and/orRWMC facilities.Given what is known about the nature and extent of non-radiological contamination andthe cleanup activities planned or carried out at INEEL, it is not expected that muchcontamination, if any, will ever reach the Valley in the future. Evenif contamination did reach the area, it would be sodiluted that the levels would be well below safeguideline values. If any contaminants traveledwith groundwater off site, they would travelsouth-southwest from INEEL, toward Minidoka(which is not in the direction of the Magic Valley,but 50 miles east of the eastern boundary of theMagic Valley Area), which is 73 miles from theINEEL source (Johnson 2000). ATSDR’s estimatessuggest that groundwater leaving INEELwould reach Minidoka in about 50 to 220 years, atwhich point its contaminants would be present atless than 0.02% of their original concentration andnot at levels sufficient to make people sick.

Gross alpha and beta measurements are screened in groundwater as a general indicatorof radiological contamination. Screening identified gross alpha and gross beta activityin groundwater beneath INEEL. High levels were found on-site at the INTEC area,where gross alpha (4,700 pCi/L, or 173 becquerels per liter [Bq/L])) and gross betaconcentrations (949,000 pCi/L, or 35, 113 Bq/L) exceeded their respective MCLs.

Groundwater samples have been further analyzed to identify the specific radionuclidesresponsible for the elevated alpha and beta radioactivity. Table A-2 in Appendix Apresents the maximum concentration of specific radionuclides detected at INEEL. Ofthe radionuclides exceeding ATSDR's CVs or EPA's MCLs, tritium and strontium-90were detected most frequently and/or in the highest concentrations. The followingdiscussion describes the occurrence of tritium and strontium-90 in the groundwater ingreater detail.

Elevated tritium levels up to 75,000 pCi/L, or 2,793 Bq/L, were detected beneath theINTEC and TRA facilities. Tritium was injected with wastewater into a disposal well atINTEC and discharged, with the wastewater, to the infiltration ponds at INTEC and theTRA. Routine use of the disposal well ended in February 1984. Since that time most ofthe radioactive wastewater was discharged to the infiltration ponds (DOE 1999). Today,INEEL disposes of much less tritium in the infiltration ponds.

A large plume extends from the INTEC and TRA areas southwestward, in the generaldirection of groundwater flow. The plume has also spread under the CFA. Tritium is theplume's primary contaminant. The plume has decreased from 51 square miles (mi2) in 1985 toabout 40 mi2 in 1991. Although the tritium concentrations have remained nearly unchanged since 1991, the higher concentration lines appear to have"receded" to the source areas at INTEC and the TRA (DOE 1999). Dilution and radioactive decay (tritium has a relatively short half-life of 12.5 years) have greatly reduced the contaminant concentrations at the edge of the plume, giving theimpression that the plume has receded (INEEL 2000). Today, the plume is monitored, butit is not actively remediated. As long as no further contamination enters the groundwater,it is expected that natural attenuation, dispersion, and decay will reduce the tritium in thegroundwater to safe levels within 100 years. Researchers are looking at ways to reducecontamination entering the groundwater, such as by reducing the amount of water thatcan seep into the ground at disposal areas. The plume will continue to be monitored todetermine the need for future cleanup (INEEL 2000)

The USGS monitors wells (USGS wells 103, 105, and 108) along INEEL's southernboundary and downgradient of the tritium plume. Tritium in these wells has beendetected in only trace amounts, well below EPA's MCL of 20,000 pCi/L, or 740 Bq/L(USGS 1997). Tritium concentrations in groundwater are expected to decrease further,because the INTEC disposal well is no longer used and less tritium is being disposedof at INEEL.

A strontium-90 plume has formed in the SRPA beneath the INTEC facility, extendingsouthwest with the general direction of groundwater flow. Concentrations have reached516,000 pCi/L, or 19.092 Bq/L (ATSDR 2000). Strontium-90 entered the groundwater asa consequence of past waste disposal practices. Between 1952 and 1995, about 24 Ci ofstrontium-90 were contained in wastewater injected directly into the SRPA through theINTEC disposal well and discharged to infiltration ponds (USGS 1997). In addition, 33Ci of strontium-90 contained in wastewater were discharged into a pit at INTEC.

Scattered detections of strontium-90 have also been reported at the TRA, but at lowerconcentrations (up to 1.9 pCi/L [0.07 Bq/L] in SRPA groundwater samples and up to179 pCi/L [6.6 Bq/L] in the perched aquifer) than at the INTEC facility. Strontium-90 in the TRAdoes not appear to be moving in a plume. Strontium-90 in the groundwater beneath theTRA is believed to be related to radioactive waste percolating down to the groundwaterfrom the infiltration and evaporation ponds.

Until 1992, strontium-90 concentrations in groundwater were decreasing as a result ofradioactive decay processes and dilution with water recharging from the Big Lost River.More recently, however, strontium-90 concentrations in most wells have remainedrelatively constant, between 2.6 ± 0.7 and 76 ± 3 pCi/L (compared to EPA's MCL of 8pCi/L [0.3 Bq/L]). It is possible that the recharge entering the groundwater from the BigLost River has decreased and that, therefore, the groundwater and associatedcontaminants are less diluted (USGS 1997).

Gross alpha and beta radioactivity levels have been routinely monitored in on-siteproduction wells and distribution systems. The detected levels of gross alpha and betaare generally consistent with background concentrations and are below their EPAMCLs (15 pCi/L, or 0.6 Bq/L, for gross alpha and 5 pCi/L, or 0.2 Bq/L, for grossbeta).

Over the years, monitoring has frequently detected tritium in certain on-site wells anddistribution systems. While most of the detections have been at levels below EPA's MCLof 20,000 pCi/L (740 Bq/L), tritium levels in the CFA #1 well during the mid- to late-1980s reached levels up to 38,900 pCi/L, or 1,493 Bq/L, above EPA's MCL (ESRF 1988,1989, 1990, 1991). Because the CFA lacks a source of tritium, it is believed that thetritium may have come from contaminated groundwater at the INTEC facility.

The CFA distribution system was not sampled before 1990; therefore, ATSDR does notknow what levels of tritium might have been delivered to the taps. It should be noted,however, that water from well CFA #1 would have been mixed with water drawn fromwell CFA #2 during that time period, and that tritium levels in the CFA #2 well weresafely below EPA's MCL. Since 1989, the tritium levels in the CFA #1 well have fallenbelow EPA's MCL (ESRF 1998). The tritium levels in both CFA wells and the CFAdistribution system currently meet water quality criteria.

Production wells near the strontium plume originating at INTEC have also been regularlymonitored for strontium-90. Strontium-90 has been detected at levels up to 1.1 pCi/L(0.04 Bq/L), below EPA's MCL of 8 pCi/L (0.3 Bq/L). Strontium-90 was not detected atall during most recent monitoring events.

Table 4.

Maximum Concentrations of Radionuclides in Drinking Water Supply Wells
Radionuclide Drinking Water Wells in CFA EPA MCL pCi/L (Bq/L)
Maximum Concentration pCi/L (Bq/L) Location Date
Tritium 38,900 (1,439) CFA # 1 1987 20,000 (740)

Source: ESRF 1998.
Bq/L = bequerels per liter; pCi/L = picocuries per liter

Historical groundwater sampling has identified very low levels of three radionuclidesbeyond site boundaries: tritium, iodine-129, and chlorine-36. In 1985, tritium detectionwas reported for several monitoring wells located just south of the site boundary. Thelevels were below EPA's MCL of 20,000 pCi/L (740 Bq/L). By 1988, the leading edge ofthe tritium plume had receded to within site boundaries. In 1992, iodine-129 was reportedin two wells about 4 and 8 miles from the southern site boundary. The detected levelswere well below 1 pCi/L (0.04 Bq/L), EPA's MCL for iodine-1291. The U.S. GeologicalSurvey (USGS) has identified chlorine-36 as being significantly above background in 1984 at well USGS 14. USGS 14 is locatedapproximately seven miles south of the southern INEEL boundary and southeast of BigSouthern Butte. The elevated chlorine-36 values at the well have been correlated todischarges at INTEC by evaluation of chlorine isotope data in other wells. These isotopeshave not been detected in more recent samples.

The USGS and the Idaho Department of Water Resources, in cooperation with DOE,have sampled select off-site private wells and water sources. These wells are between thesouthern boundary of INEEL and the Hagerman area, and they tap into the SRPA. Theyinclude domestic wells, irrigation wells, springs, dairy wells, and stock wells. The wellshave been analyzed for selected radionuclides. Monitoring indicates that no radionuclideshave exceeded the established MCLs for radionuclides in drinking water.

During monitoring in 1998, ESRF collected 28 samples from the off-site drinking waterlocations and analyzed the samples for gross alpha and beta radioactivity particles andtritium. No samples contained detectable concentrations of gross alpha or tritium. Grossbeta activity above the minimum detectable concentration was present in many of thedrinking water samples at levels between 3.0 ± 2.0 pCi/L and 8.0 ± 3.0 pCi/L, but atlevels below EPA's MCL (50 pCi/L) for drinking water. Concentrations in this range arenormal. They are attributed to the decay of naturally occurring potassium-40, thorium,and uranium, which dissolve with water as it trickles down through the soil (ESRF 1999).

As noted in the on-site groundwater discussion, groundwater moves south-southwestfrom INEEL toward Minidoka, located 73 miles away. It could take between 50 and 220years for the water in the groundwater plume to reach the town, at which point thecontamination is expected to be greatly diluted.

Surface Waters

INEEL is located in the Pioneer Basin, also known as the Mud Lake-Lost River Basin.Because this is a closed drainage basin, surface water does not flow off site. Instead,precipitation and inflowing surface water infiltrate the groundwater underneath INEEL orthe water evapotranspires. Flooding is a concern at INEEL: facilities have been affectedin the past by a combination of rapid snow melts, heavy rains, and frozen soil thawing.To prevent flooding, a diversion dam was installed in 1958 (and expanded in 1984) nearthe southwestern boundary to divert water to a series of natural depressions and spreadingareas (DOE 1995).

Three rivers could possibly flow onto INEEL: Big Lost River, Little Lost River, andBirch Creek. Big Lost River, the major surface-water body, enters INEEL in thesouthwest corner of the site and travels northeast into an area of natural infiltrationbasins (also known as playas) in the northwest corner of the site. It drains more than1,400 mi2 of mountainous area that includes parts of the Lost River and the Pioneer Ranges (USGS 1997; LMITCO 1998). Little Lost River drains about 705 mi2 of land, and Birch Creek drains an additional 750 mi2 of land to the north and west of INEEL (DOE 1995). LittleLost River and Birch Creek are frequently used as sources of irrigation before they reach the site boundary, and therefore their waters rarely reachINEEL. However, when there is a heavy rainfall or rapid snow melt, water from these two rivers may enter INEEL from the northwest and rechargethe groundwater aquifer. Intermittent streams are also present during periods of high rainfall.

Only limited surface water monitoring has been done at or near INEEL. This pathway isnot considered a viable route for off-site contaminant transport. First, INEEL does notwithdraw or use surface water for its operations, nor does it discharge liquid waste, oreffluent, into natural surface waters. Liquid effluents generated by INEEL are dischargedto on-site sewage lagoons, seepage ponds, industrial waste ponds, industrial wasteditches, and sewage treatment facilities (ERSF 1998). Second, contaminants are notexpected to be transported off site with surface water, since rivers and creeks seldom flowbeyond site borders. As noted, most inflowing surface water and precipitation at INEELinfiltrates into groundwater. The previous section discusses groundwater quality.

Some of the information available comes from special studies by USGS of non-radiological (purgeable organic) compounds in water. The USGS data collected from sixsites at or near INEEL indicated that the surface water quality met the applicable non-radiological water quality standards (DOE 1999, ESRF 2000) and has remained fairlyconstant over the years of testing.

More in-depth surface water sampling was done in the Magic Valley area (near Twin Falls) located southwest—slightly west of the general direction of groundwater flow—of the site (ESRF 1995). This sampling was done largely to determine whether contaminants in the Snake River Plain Aquifer were resurfacing in surface water downgradient of and at a distance from INEEL operational areas. Samples were collected quarterly from the Snake River in that study area and analyzed for gross alpha and beta activity and tritium.

The monitoring results indicate that concentrations of radionuclides in the surface watersamples have generally been lower than their EPA MCLs for drinking water. Detection ofradionuclides in groundwater was likely related to naturally occurring sources for theregion. During recent sampling in 1998, eight samples from surface water locationsshowed no detectable concentrations of gross alpha or tritium. Gross beta activity abovethe minimum detectable concentration was present in a total of 32 of the 36 off-sitegroundwater and surface water samples at concentrations ranging from 3.0 ± 2.0 pCi/L to8.0 ± 3.0 pCi/L, all below the MCL of 50 pCi/L (ESRF 2000). Concentrations detected inthis range are normal and are attributed to decay of naturally occurring radionuclides,which dissolve in the water as it trickles through soil.


Past spills and former waste management practices at certain INEEL facilities haveresulted in contamination being released to the surrounding surface soil. Under WMSP,surface soil samples have been collected from the Radioactive Waste ManagementComplex, the Stored Waste Experimental Pilot Plant, and the Waste ExperimentalReduction Facility every 3 years. Under SESP, soil from eight WAGs is analyzed forradionuclides once every 7 years (ESRF 1998).

Monitoring revealed that non-radiological contaminants have been released to surfacesoil at INEEL. Detected contaminants include metals (arsenic, cadmium, and mercury),SVOCs [benzo(a)pyrene and DEHP], one explosive (2,4,6-trinitrotoluene), and PCBs(Aroclor 1254 and Aroclor 1260). Contaminants identified at levels above comparisonvalues include arsenic, mercury, benzo(a)pyrene, DEHP, 2,4,6-trinitrotoluene, andAroclor 1260, a PCB. These substances will be evaluated in the Public HealthImplications section of this PHA. Table A-3 in Appendix A summarizes non-radiological contaminant concentrations.

Radiological contamination has been detected in surface soil in restricted access areas ofINEEL. Some of the highest levels reported include americium-241 at 3,200 pCi/g(118,400 Bq/kg) and strontium-90 at 38,000 pCi/g (1 × 106 Bq/kg) in the TRA area;cesium-137 at 30,400 pCi/g ( 1.1 x 10-6 Bq/kg) in the TSF; and radium-226 at 11.9 pCi/g(440.3 Bq/kg) in the ARA.

ATSDR does not have soil comparison values for many radionuclides. In the absenceof comparison values, ATSDR analyzed the maximum concentrations of radionuclidesin on-site surface soil using the National Council on Radiation and ProtectionMeasurements (NCRP) Report No. 129 Recommended Screening Limits forContaminated Surface Soil and Review of Factors Relevant to Site-Specific Studies.

What is background radiation?Background radiation comes fromcosmic sources, from naturallyoccurring radioactive materials,and from global fallout. In theUnited States, the average annualdose from background radiation is300 mrem, of which 200 mremcomes from the natural decay ofradon. More detailed explanationscan be found in Appendix GRadiation and RadioactiveMaterial.Following this guidance, ATSDR derived screeningestimates of exposure doses. Because INEEL is in themiddle of the Arco Desert, ATSDR derived screeningestimates of doses for the sparsely vegetated pastureuse scenario. ATSDR then compared the screeningdose estimates to the International Commission onRadiological Protection (ICRP) guidance level.Currently, ICRP recommends that the general publicbe exposed to no more than 100 millirems (mrems) ofradiation (or 1 millisievert) above background per yearof exposure, based on a chronic exposure over a 70-year life span.

Background doses vary for several reasons, includingnaturally occurring sources (e.g., uranium and radon)and elevation. At sea level, the annual background dose from external sources is 100 ± 10 mrem (Eisenbud 1997). At higher elevations (INEEL is atapproximately 4,900 feet), the background dose is expected to be higher because there is lessatmosphere to provide shielding from solar and cosmic radiation.

How do we know if airborne contaminantsoriginating from INEEL have traveled offsite?Wind-borne contamination could spread eastwardfrom the INEEL site. To monitor possibleoff-site migration, INEEL collected soil,air, and biota samples at locations near theINEEL perimeter (or boundary locations), aswell at locations further away from the site(or distant locations). Boundary locations includecommunities near the INEEL boundary,including Atomic City, Arco, Monteview,Taber, and Terreton. While ATSDR refers tothese communities as boundary communities,there is a buffer of at least 6 miles between anyboundary community and the nearest INEELfacility or Waste Area Group. Distant locationsinclude communities further away, such asAmerican Falls, Blackfoot, Carey, Dietrich,Idaho Falls, and Minidoka.ATSDR compared the boundary and distantsamples to samples collected at INEEL as ameans of better distinguishing betweenpossible INEEL contributions from othersources (e.g., worldwide fallout, long-livednatural radioactivity). Contaminationoriginating at INEEL would be expected todecrease with distance from the source, orbetween boundary and distant locations.Table A-4 lists the maximum concentrations of radionuclides detected at INEEL, thelocations and years of the detections, and the screening estimate of doses based on themaximum detected concentrations. As the table shows, exposure dose estimates based onthe maximum detected concentrations exceeded the ICRP guideline of 100 mrem foramericium-241 (88 mrem), cesium-137 (65,238 mrem), radium-226 (251 mrem), andstrontium-90 (632,700 mrem). As noted, the highest levels of americium-241 andstrontium-90 were found in the TRA, and the highest level of cesium-137 was found inthe TSF. These concentrations are most likely related to hot spots of contaminationcaused by past operations. The high concentrations of radium-226 may be natural:INEEL's activities did not call for radium at the parts of the site where radium was foundin soil.

In all likelihood, the greatest part of a person's time would not be spent on soil containingthe highest detected concentrations of radionuclides. ATSDR therefore further analyzedthe levels of americium-241, cesium-137, radium-226, and strontium-90 in on-site soil byusing the geometric mean of the soil concentrations. (A geometric mean is used whendata show a wide range of concentrations.) The geometric mean and the estimated dosesare presented in Table A-5. As noted, the screening doses based on the geometric mean concentrations (americium-241, 0mrem; cesium-137, 5 mrem; radium-226, 41 mrem; strontium-90, 43 mrem) are below the ICRPguidance value of 100 mrem.

Since the 1970s, INEEL has monitored surface soil at boundary and distant off-site locations and analyzed samples for specific radionuclides. (From 1970 through 1976, samples were collected annually—except in 1972—and from 1978 on, samples have been collected biannually.)

Radionuclides were detected much less frequently and in much lower concentrations (sometimes by as much as several orders of magnitude) in off-site samples than in on-site samples. Of the radionuclides analyzed, americium-241 (up to 0.09 pCi/g, or 3.3 Bq/kg), cesium-137 (up to 1.2 pCi/g, or 44.4 Bq/kg ), plutonium-238 (0.0027 pCi/g, or 0.1 Bq/kg), and plutonium-239/-240 (up to 0.035 pCi/g, or 1.3 Bq/kg) were detected (ATSDR 2000). Off-site concentrations typically varied little by location (boundary versus distant) or by sampling year (ESRF 1999).

Contamination leaving INEEL would be expected to decrease with distance from the source. But concentrations were nearly uniform, with no consistent correlation with distance from the INEEL boundary. Similarly, INEEL-derived contamination should have been highest shortly after the times of INEEL's greatest release. But again, off-site concentrations varied little from year to year. It is possible that radionuclides detected off-site are the result of fallout from worldwide nuclear weapons testing.

ATSDR further analyzed the maximum concentrations of radionuclides in off-site surface soil using the NCRP Report No.129 Recommended Screening Limits for Contaminated Surface Soil and Review of Factors Relevant to Site-Specific Studies, then compared the screening dose estimates to the ICRP recommended value of 100 mrem. The estimates, which assumed exposure to the maximum off-site concentration of radionuclides, were much lower than the ICRP guideline of 100 mrem: americium-241, 0 mrem; cesium-137, 3 mrem; plutonium-238, 0 mrem; plutonium-239/-240, 0 mrem; strontium-90, 10 mrem.


Non-radiological air pollutants have been emitted from INEEL facilities and operations. INEEL monitors relevant INEEL facilities for (1) criteria pollutants (such as nitrogen dioxide, sulfur dioxide, carbon monoxide, and ozone); (2) toxic air pollutants (such as benzene, carbon tetrachloride, formaldehyde, fluorides, ammonia, and hydrochloric and sulfuric acids); and (3) particulate matter. Combustion activities (e.g., boilers and emergency generators) and chemical processing operations at INEEL emit mostly gaseous and vaporous pollutants. Waste management processes, construction, and excavation activities mostly generate particulate matter (DOE 1995).

Pollutants of particular interest are two oxides of nitrogen, nitrogen oxide (NO) and nitrogen dioxide(NO2), which are collectively referred to as NOx. Other substances monitored includesulfur oxides (primarily in the form of sulfur dioxide, or SO2) and particulates greaterthan 10 and 2.5 micrometers in diameter( PM-10 and PM-2.5). VOCs and NOx areevaluated for their potential to contribute to ozone formation.

NO2 was monitored at Van Buren Avenue and the Experimental Field Station (EFS)through 1998. At Van Buren, quarterly mean concentrations ranged from 1.9 microgramsper cubic meter (µg/m3) to 3.4 µg/m3, with an annual mean of 2.7 µg/m3 (1.5 ppb). Thisannual concentration is 3% of the EPA air quality standard of 100 µg/m3 for NO2. Themaximum 24-hour concentration measured was 7.1 µg/m3 (3.8 ppb) on December 15.Quarterly means at EFS sampling ranged from 2.3 µg/m3 during the fourth quarter to 16.1µg/m3 during the first quarter. For 1998, the mean concentration was 7 µg/m3 (3.9 ppb), 7%of the EPA standard. The maximum 24-hour average concentration occurred on January14, when a value of 19.2 µg/m3 (10.2 ppb) was recorded.

EFS is thought to be affected by the New Waste Calcining Facility at INTEC, the largestsingle source of NO2 at INEEL. The Experimental Field Station (EFS) is about 3 miles inthe prevailing wind direction from INTEC. NO2 concentrations observed there mayindicate some effect from this facility on ambient concentrations. All quarterlyconcentrations have remained below 50% of the annual standard from 1990 though 1998(time period of monitoring). Except in 1993, all annual NO2 levels remained below 20µg/m3. 1993 levels peaked at approximately 50 µg/m3.

SO2 was monitored at the Van Buren Avenue location. The mean SO2 concentration for1998 was 7.5 µg/m3 (2.8 ppb), 9% of EPA's annual primary air quality standard of 80µg/m3. In 1998, the maximum recorded 24-hour SO2 concentration at Van Buren was 25.6µg/m3, which did not approach the EPA secondary primary air quality standard of 365µg/m3. In addition to the two primary standards, there is a secondary ambient air qualitystandard for SOx that cannot be exceeded more than once per year. The highest 3-hourconcentration was 33.3 µg/m3 (12.5 ppb), approximately 2.6% of the secondary standardof 1,300 µg/m3.

Mean SO2 concentrations have decreased in the past decade. In 1989, INEEL's meanconcentration was 17 ± 2 µg/m3. In 1998, the mean concentration was 8 ± 1 µg/m3.LMITCO gathered INEEL particulate concentrations in 1996; its maximumreading–which came from the RWMC–was 35 µg/m3 (ESRF 1997), less than themaximum 24-hour concentration of 150 µg/m3.

In addition, INEEL monitored for specific chemical contaminants at the CFA and theRWMC (ATSDR 2000). Nineteen of the listed contaminants exceeded ATSDR's CVs(see Table A-6), but these were actually measurements of subsurface vapor concentrationand not ambient air. The only two chemicals that did not exceed their comparison valueswere benzene and trans-1,2-dichloroethene, which were detected at the CFA. For 14 ofthe 21 chemicals monitored, the maximum concentrations were detected at the RWMC.At this location, the values ranged from 4,520 milligrams per cubic meter (mg/m3) oftoluene to 20,800,000 mg/m3 of carbon tetrachloride. At the CFA, the concentrationsranged from 31.7 mg/m3 of trans-1,2-dichloroethene to 18,600 mg/m3 of 1,1-dichloroethene.

Even though certain non-radioactive airborne contaminants have been detected atelevated concentrations on the INEEL site, concentrations are expected to decreasegreatly by the time they reach the INEEL boundaries, six miles away. Still, the DOEmeasured particulate matter, nitrogen dioxide, and sulfur dioxide at off-site locationsaround INEEL. Results of the monitoring indicate the levels are within air qualitystandards set by the EPA (INEEL 2000). Over the years, particulate concentrationshave generally been higher at boundary and distant locations than at INEEL. Forexample, in 1998, the annual means of total suspended particulate concentrationsranged from 5 µg/m3 at INEEL's ARA to 40 µg/m3 at Arco.

Small radioactive particles can be carried in the air. Therefore, DOE established anambient radiological air monitoring program at INEEL in 1952 with monitoring of theRWMC area. The program was intended to determine worker safety and identifycontamination controls at points of releases. Airborne particulate radioactivity andspecific radionuclides are also now routinely monitored by a network of stations locatedon site, around the site (upwind and downwind of the site), and at boundary and distantlocations. The sampling locations are selected to provide information on possiblemigrating pollutants before they can become a concern for off-site residents.

Particulates are monitored continuously on the INEEL site by use of a network of low-volume air samplers at on-site stations, boundary locations, and distant locations. INEELselected on-site sampler locations to give adequate coverage in the event of releases ofradioactivity from INEEL facilities and to give adequate time to protect the off-site publicin the event of releases. Each low-volume air sampler is made up of a set of filtersconsisting of a 1.2-micrometer (µm) pore membrane filter followed by a charcoalcartridge. The filters are 99% efficient for airborne particulate radioactivity and iodides(ESRF 1999).

The filters from the low-volume air samples are collected and analyzed weekly for grossalpha and gross beta activity. If any traces of radionuclides are detected, the filters arethen individually analyzed for gamma-emitting radionuclides. The particulate filters arealso composited by location at the end of each quarter; all on-site composites areanalyzed for gamma emitters by gamma spectroscopy, and one third of off-sitecomposites are analyzed for specific radionuclides, which include americium-241,plutonium-238, and strontium-90.

Annual average concentrations of gross alpha and gross beta through 1998 have remainedrelatively low, below their respective DOE-derived concentration guides (DCGs) of 2 ×10-15microcuries per milliliter ( µCi/mL)2 and 3 × 10-15 µCi/mL. DOE's DCGs are derived formembers of the general public based on the most restrictive alpha and beta emittersresulting in an effective dose equivalent of 100 mrem per year. Airborne tritium possiblyrelated to activities at INEEL has been detected, but at levels below DOE's DCG of 10-15 µCi/mL. Particulate matter detected in certain areas, such as the RWMC and INTEC, maybe attributed to the slightly contaminated soil suspended in the air during constructionactivities.

During recent sampling (1998), gross alpha was present in on-site samples (annual meanconcentration of [1.1 ± 0.1] × 10-15 µCi/mL), in boundary samples (annual mean concentration of [1.2 ± 0.1] × 10-15 µCi/mL), and in distant samples (annual mean concentration of [1.5 ±0.1] × -15 µCi/mL). Likewise, gross beta was measured in on-site samples (annual meanconcentration of [24 ± 1] × 10-15 µCi/mL), in off-site boundary samples (annual meanconcentration of [23.1 ± 1] × 10-15 µCi/mL), and in distant off-site samples (annual meanconcentration of [21 ± 1] × 10-15 µCi/mL). All detected concentrations were below DOEDCGs for gross alpha and gross beta. The detected levels of airborne radioactivity for on-site, boundary, and distant locations were similar throughout the year, suggesting that noone area was being impacted by airborne contributions from specific sources, such as theINEEL facility (ESRF 1999).

To identify specific radionuclides that might have contributed to elevated concentrationsin 1998, particulate filters were composited by location at the end of each quarter andanalyzed for plutonium-238, americium-241, and strontium-90. Of the specificradionuclides analyzed by this method, only americium-241 and strontium-90 weredetected. Americium-241 was measured during the first quarter of the year at two off-sitelocations, Blackfoot ([1.9 ± 1.5] × 10-15 µCi/mL) and Arco ([2.1 ± 1.5] × 10-18 µCi/mL), andthen during the third quarter at one on-site location, ANL-W ([10 ± 5.71] × 10-18 µCi/mL).Strontium-90 was detected during the second and third quarters at on-site locations atconcentrations up to (16 ± 7.7) × 10-11 µCi/mL (at the TRA) and during the third quarter atoff-site locations at concentrations up to (13 ± 8.5) × 10-11 µCi/mL (at Blackfoot). All theselevels are below DOE DCGs.

Contamination from INEEL should decrease with distance from the source. Butconcentrations in the ambient air and particulate samples showed little variation withdistance from the INEEL boundary. Similarly, INEEL-derived contamination shouldhave been greatest just after the times of INEEL's greatest release, but off-siteconcentrations varied little from year to year. Sources other than INEEL, such asworldwide fallout, may be the origin of the detected radionuclides (ESRF 1999).

Atmospheric moisture samples and precipitation samples are collected during certainyears and evaluated for the presence of tritium. Detected tritium concentrations havegenerally been low, within normal ranges observed worldwide, and have varied little bylocation. During recent sampling in 1998, 31 atmospheric samples were taken at four off-site locations (Atomic City, Blackfoot, Idaho Falls, and Rexburg). Only five of thesesamples indicated any positive detects for tritium (up to [4.9 ± 2.0)] × 10-15 µCi/mL).Tritium was also detected (up to [4.9 ± 1.1] × 10-7) µCi/mL) in 4 of 49 samples taken fromtwo on-site locations (weekly sampling at EFS and monthly sampling at CFA) and fromone off-site location (monthly sampling at Idaho Falls). Again, measured levels werewithin acceptable ranges, suggesting that the tritium's presence could have resulted fromnatural production in the atmosphere or from worldwide fallout (ESRF 1999). (SeeAppendix G for a description of radiation and worldwide fallout.)


Contaminants released from INEEL to air may accumulate in plants and animals, whichare collectively referred to as biota. Many of these plants and animals are importantsources of human nutrition, but people who consume them may be potentially exposedto chemical and radiological substances.

INEEL is home to a broad range of wildlife. Game species seen at INEEL include deer,moose, and elk. Other large animal species include coyotes and bobcats. In addition tothese mammals, INEEL supports a large variety of smaller animals and some species offish, such as kokanee salmon and rainbow trout, which are present when the Big LostRiver flows onto the site as a result of heavy rains or melting snow runoff (DOE 1995).Controlled hunting is permitted at INEEL one-half mile inside the site boundary. Thehunting helps the Idaho Department of Fish and Game reduce crop damage caused byforaging wildlife. Cattle and sheep graze on 300,000 to 350,000 acres of INEEL bufferzone (DOE 1995), but the animals are not allowed within 2 miles of any nuclear facility,and dairy cattle are not permitted to graze on any of the buffer zone. Several farms andcommercial and single-family dairies at off-site locations grow crops and raise dairycows.

Surveillance of biota is conducted at INEEL in select facilities (e.g., RWMC andWERF) and off-site. Most of the monitoring is for radionuclides, with limitedmonitoring of selected metals in some vegetation, wildlife, and other biota. ATSDR hasevaluated the results of metals analyses for certain types of vegetation, primarilysagebrush, and animals, such as rabbits, mice, and insects. The samples did not containhigh enough levels of metals to make people ill (ATSDR 2000). Off-site sampling ofbiota and locally grown foods conducted by ESRF has focused exclusively onradionuclides.

Cows graze over large areas of pasture or range, and their milk tends to concentrateradioactive iodine. As such, small levels of radioactive particles can translate to highconcentrations in milk. Children are particularly vulnerable to the effects of iodine inmilk: they drink more milk than adults, their thyroids glands are smaller (where iodineconcentrates), and children tend to be more sensitive to contaminants than adults.Sampling of milk from dairies near the INEEL border and distant from INEEL, however,show that iodine-131 was within levels seen in the environment and that no otherradionuclides were present (ESRF 2000). Milk samples are also analyzed for strontium-90 and tritium.

Other biota routinely analyzed for radioactivity and specific radionuclides are wheat andgarden lettuce. Potatoes have also been sampled during selected years.) Samples havebeen collected from both boundary locations near the site and from distant locationsfurther away. Boundary samples have been compared to distant samples to identifypossible influences from INEEL operations. Tissue samples from sheep and game thatgraze at INEEL have also been analyzed (ESRF 1999). Radionuclide concentrations infoodstuff have been low, with little variation between sampling locations (boundaryversus distant) or between years (from 1988 through 1998). Of the radionuclides tested,strontium-90 was detected most frequently in the tested crops. As with the otherradionuclides, strontium-90 concentrations in crops did not vary greatly from boundaryto distant sampling locations or by year (ESRF 1999).

Cesium-137 was the most commonly detected radionuclide in tissue samples taken fromsheep and local game animals. Cesium-137 concentrations detected in 1998 in three ofthe four tissue samples from sheep measured between (4.1 ± 3.4) × 10-9 µCi/g and (7.0 ±3.5) × 10-9 µCi/g, and were similar to those found at both on-site and off-site controlsamples during recent years (1994 through 1997). Concentrations in samples collectedfrom game animals (elk, pronghorn antelope, mule deers) ranged from (2.3 ± 2.1) × 10-9 µCi/g to (16.9 ± 2.6) × 10-9 µCi/g. The Cs-137 concentrations appear to be higher than theDOE DCG of 4 x 10-10 uCi/mL for class D (DOE Order 5100.5, 2-8-90, page III-14).ATSDR's Toxicological Profile for Cesium identifies cesium-137 levels in Alaskancaribou meat, in the range of (7 to 63) x 10-7 µCi/g (ATSDR 2001). Levels measured atINEEL could be considered as being attributable to ambient levels from previousatmospheric nuclear detonations.

Contamination from INEEL would be expected to decrease with distance from thesource, but concentrations in the samples showed little variation with distance from theINEEL boundary. Similarly, INEEL-derived contamination should have been greatestjust after the times of INEEL's greatest release, but off-site concentrations varied littlefrom year to year. Sources other than INEEL, such as worldwide fallout, may be theorigin of the radionuclides in the biota tissue samples.

Ambient Radiation

Atmospheric transport is a viable pathway by which people in the surroundingcommunity could be exposed to radionuclides released from INEEL. Measuring devicescalled thermoluminescent dosimeters (TLDs) were placed at and near INEEL andmonitored for radiation exposure by INEEL and independent researchers at ESRF(ESRF 2000).

The type of radiation that the TLDs measure is known as external radiation. Thisclassification is an important distinction, because the total dose of radiation a personmight incur includes both doses from external sources and doses from internal sources.External doses result from radioactive sources outside the body; internal radiation dosesresult from exposure to radioactive sources inside the body. Whether an exposurecontributes to a person's external or internal dose depends primarily on the type ofradiation. Alpha particles cannot travel far, and the skin prevents them from entering thebody. Therefore, exposures to alpha particles would not contribute to a person's externaldose; if an alpha particle source is within the body, it would contribute to a person'sinternal dose. Beta particles also may be responsible for both internal and external doses,but they do not penetrate body tissue as easily as gamma rays, limiting the dose fromexternal sources. Gamma rays can travel long distances and can easily penetrate bodytissues; therefore, people can be exposed to gamma rays through external or internalsources.

The external radiation that TLDs check could have many sources–natural radioactivityin the air and soil, cosmic radiation from space, fallout from nuclear weapons tests,radioactivity from fossil fuel burning, or radioactive effluents from INEEL operations andother industrial processes. TLD cards were placed 3 feet above the ground at 135locations along facility perimeters, largely in areas likely to show the highest gammaradiation readings. The cards at each TLD location are replaced twice a year to providesemi-annual cumulative external gamma radiation measurement. More recently, cardshave also been placed at 13 off-site locations (ESRF 2000).

Radiation dose measured by the TLDs is expressed in millirem (mrem). Gamma radiationmeasurements at on-site TLDs have generally stayed below 200 mrem/year.Occasionally, there were high readings near on-site radioactive material storage areas atthe INTEC facility, near the TRA, and near a former radioactive disposal pond (ESRF1995). In 1998, on-site TLD readings were highest at the INTEC facility (233 ± 9 mrem),at the RWMC (231 ± 8 mrem), and at the TRA (up to 574 ± 58 mrem) (ESRF 2000).

Lower measurements have been recorded at off-site TLDs. The average dose of externalradiation at boundary locations was equivalent to about 126 mrem and is consistent withbackground. The expected annual background dose from external (terrestrial and cosmic)sources is roughly 140 ± 15 mrem, because the area is about 4,900 feet above sea leveland there is less atmosphere to shield from solar and cosmic radiation than at sea level. Atsea level the annual background dose from external sources is closer to 100 ± 10 mrem(Eisenbud 1997).

1 Iodine-129 has a very long half-life of 15.7 millions years, suggesting that it may remain present in the environment for a long time. For this reason, scientists are interested in tracking iodine-129 concentrations in groundwater. Data, however, are too limited at this time to showcontaminant trends.
2 1 × 10-9 µCi/mL = 1 pCi/L = 1,000 pCi/m3.

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